On July 1, the main mission of the Dawn probe came to an end. NASA is not going to stop the operation of the device, like . But Dawn will not fly further than Ceres, as expected. Previously, the project team planned that the probe, after studying the planetoid Ceres, would fly further - first to the Sun, entering a safe orbit, and then to the asteroid Adeona. The last point of the plan was scheduled for May 2019.
But now experts have come to the conclusion that the study of Ceres is worth continuing - the scientific value of the current mission will be higher than visiting Adeona. Scientists believe that Dawn will be able to obtain scientifically interesting data when the planetoid passes through perihelion, the point of its orbit that is minimally distant from the Sun. The project team could not come to a common agreement in terms of extending the probe’s mission. On July 1, a post appeared on NASA’s website with information about Dawn’s flight to Adeona. A little later, the post was removed, and agency representatives stated that the publication of this material was a mistake. The website now contains information that the probe remains in Ceres orbit. 
Photos of spots on Ceres sent by Dawn in March 2016 (photo: NASA)
The Long Road to Ceres
The history of the Dawn probe began in 1992, when project lead specialist Christopher Russell introduced the device's efficient ion engines. They cannot develop as much thrust as rocket engines, but they operate much longer. Such engines were initially planned to be installed on artificial Earth satellites, but Russell decided to put them on a device that would go to the asteroid belt of the Solar System.The authors of the project received three refusals from NASA management, but in 2001 the mission was still approved. As part of the mission, the Dawn probe would visit two of the largest objects in the asteroid belt: Vesta, the largest asteroid in the solar system, and Ceres, a dwarf planet. According to Russell, using chemical rocket engines to Vesta and Ceres would require launching two devices - there simply would not be enough fuel to visit two objects in the asteroid belt at once. But because the project team decided to use ion engines, the entire program could be completed using just one vehicle.
Why did you decide to choose Vesta and Ceres for study? The fact is that scientists considered them to be the oldest objects in the solar system. Their study would help clarify some aspects of the origin of the planets and find out what processes led to the formation of the Solar System in its current form. Moreover, both objects are different from each other. Vesta is a rocky world without much liquid or gases. The surface of Vesta is covered with meteorite craters. Ceres differs from Vesta in its lower density; previously it was suggested that its surface could be covered with ice, and an ocean of liquid water could be hidden under the surface. In addition, astronomers noticed mysterious bright spots on the surface of Ceres. But from Earth it was impossible to understand what these formations were and what their nature was. Ceres is the only object in the solar system with such properties.
Dawn mission successes
The probe was launched into space in 2007. The launch of the device beyond the Earth was carried out using a Delta II launch vehicle. The device approached Vesta in 2011.
Antonia Crater (southern hemisphere of Vesta). Photo: NASA
After spending a year in orbit of the asteroid, the probe set off for Ceres. The planetoid Dawn entered orbit in March 2015. In October 2015, the spacecraft entered its lowest orbit.
As they got closer to the planetoid, Earth scientists received better and better images of Ceres and its surface. But the nature of the spots was determined only after the closest approach to the planetoid. Until this point, one group of scientists had suggested that the spots were water ice coming to the surface. Other experts argued that this was the release of salts to the surface.
After the probe sent the latest data from studying the spots with high-resolution photographs of these formations, the situation became clearer. Most likely, the spots consist of magnesium sulfate, a chemical compound with a high albedo. By the way, not so long ago scientists were working on these spots.
Scientists have found that under the surface of the planetoid there are large reserves of water ice. Scientists say that in the early stages of its evolution, Ceres was a warm world, with an ocean splashing on its surface. Unfortunately, over time, this world began to cool down. And since the planetoid did not have its own heat source (like Europa, for example), the water froze.
What's next?
The Dawn probe will continue to study the planetoid while in its orbit. There are more questions about the origin of Ceres, about the structure of its surface layers and subsurface than there are answers. And scientists hope to get answers to at least some of these questions.Ceres is the largest asteroid in the asteroid belt, which has received the status of a dwarf planet. The pursuit of the discovery of this planet began in 1781, at the time when the planet Uranus was discovered, located in the very region of space in space that belonged to the Titius-Bode rule. Titius's rule (German scientist) proves the pattern of increasing increase in the radii of the orbits of planets located near the Sun. Some time later, this rule turned out to be inaccurate, and the discovery of Uranus in the same place gave rise to an avid “hunt for the planets” among astronomers of past centuries.
History of discovery
Later, in 1800, an international group of scientists - astronomers “Heavenly Guard” was founded. Around the clock, she observed the space in space between the orbits of Jupiter and Mars, that is, in the area where that yet undiscovered planet should have been located. Ceres was discovered in this area by the Italian astronomer Giuseppe Piazzi in 1801. At first he mistook it for a comet, but still noticed that it had certain features. Throughout the year, other scientists also attempted to document the existence of this asteroid planet, but only on the last day of 1801 were they able to confirm its existence. With this, the Titius-Bode rule again became valid. Giuseppe Piazzi himself named the asteroid planet “Ceres,” although before that it was pronounced “Ferdinand’s Ceres.”
In 1802, Ceres was classified as an asteroid. The largest cosmic body in the main asteroid belt has a diameter of 950 kilometers, has the shape of a sphere, which arose due to the presence of Ceres’s own gravity, and six thousand times less mass than the Earth has, and at the same time makes up a third of the total mass of objects asteroid belts.
According to scientists' research, after the asteroid Ceres acquired a spherical shape, processes of gradual displacement of the heaviest rocks into the central part began to occur. The result of this displacement was the formation of a stone core. Water ice makes up the outer shell, which is about 100 kilometers thick, which exceeds the fresh water reserves on Earth.
Research
Ceres is one of the main participants, with good prospects, in projected space developments. First of all, this is due to the fact that it stores a huge supply of fresh water and this fact may mean that there is an opportunity to create life here.
From a colonization perspective, Ceres is of great interest. At the second stage of space exploration, they plan to colonize Ceres. At the first stage, they expect to colonize space objects located relatively close to the Earth, Moon, Venus, Mars, and Mercury.
Distant future
Ceres is located between the gas giants and the terrestrial planets; it has good conditions, allowing it to serve as an ideal transit point for the creation of space bases on it. The negative factors of this planet include low gravity and the absence of a magnetic field, which is a negative factor for human health.
Animation of the DAWN spacecraft flying from Vesta to Ceres
Ceres was discovered on January 1, 1801 by the Italian Giuseppe Piazzi. It is the only object in the asteroid belt that can be seen with the naked eye under certain conditions.
In 2006, Ceres was classified as a dwarf planet, that is, a celestial body whose dimensions allow it, under the influence of internal forces, to take a shape close to spherical. It is very important that the study of Ceres by the Dawn probe will be carried out with the same equipment as Vesta, and therefore the results obtained will be easily comparable with each other.
Surface map
Research program
In the process of researching Ceres, all the equipment available at the station, previously used in the study of Vesta, will be used. These are photographic equipment, a spectrograph and a radiation detector. In addition, using radio measurements, the gravitational field of the celestial body will be assessed, which will make it possible to determine the change in density inside it and thus determine whether Ceres has a metallic core. At the lowest orbit, a new method of controlling the vehicle, called “hybrid”, will be tested using flywheel engines similar to a gyroscope. The purpose of the experiment is to save hydrazine for use in unforeseen cases.
Approximate research schedule
According to scientists' plans, the spacecraft will enter the gravity zone of Ceres in early April 2015. Having approached 4,430 km and entered a circular orbit, the station will begin a 22-day program of exploration of the dwarf planet. Then there will be a decrease to 1480 km and work will continue. The lowest orbit to which the aircraft is planned to be lowered is approximately 375 km. The probe should spend about three months on it. Further, the situation will develop depending on the accuracy of the implementation of the previous stages, the presence of hydrazine in the fuel tanks and the remaining supply of electricity in the nickel-hydrogen battery.
Photographing
Photographing the celestial body will begin as soon as the aircraft approaches it at a distance of 13,500 km. Already from this height, Ceres looks 8 times larger than the Moon. Research will intensify as the space probe descends into lower circular orbits. Sequential photography, first from an altitude of 4430 km, then 1480 and at the final stage – 375 km, which will be carried out for almost six months, will create an initial overview and then a detailed map of all areas of the dwarf planet. During this time, thousands of photographs will be taken, which will gradually be transmitted to Earth.
Data transmission to Earth
Gallery of Deep SpaceNetwork antennas.
The spacecraft will begin communicating with the Earth as soon as the first information for transmission appears. Data will be sent selectively, viewed in the control center, and only after that a command will be given to send the rest. This is done in order to obtain the most relevant information first. The data will be pre-compressed, since the transfer speed is low by earthly standards. In addition, the design transmission speed (41–128 kbit/s) may become significantly lower due to technical problems, as has already happened in the Vesta area. Then the main antenna failed, but scientists managed to restore its functionality. The probe's data will be received by the largest and most powerful deep space communications system, Deep SpaceNetwork.
Special Expectations
A number of scientists suggest that Ceres consists of 25% water, which exceeds all available terrestrial reserves, and some of it may be in the liquid phase under 100 kilometers of ice. This is a hypothesis for now, but there is not much time left to wait before it is confirmed or refuted. Until now, scientists have not been able to find celestial bodies with liquid water, which naturally fuels interest in the expedition of the Dawn space probe. The presence of large reserves of ice on the way to other planets of the Solar System opens up the possibility of using it for the needs of future manned expeditions.
The Dawn spacecraft continues its leisurely exploration of the asteroid Ceres. So, on Friday, October 23, he carried out the next activation of the ion propulsion system in order to move to the fourth and final scientific orbit around this asteroid belt object. Currently, the device has successfully completed its two-month research work at an altitude of 1,470 kilometers from the surface of Ceres and transmitted a variety of information to Earth.
In the new orbit, Dawn will continue to map Ceres, and the device will descend to it for more than seven weeks. The final height above the surface will be only 380 kilometers. Sometime in mid-December 2015, Dawn will begin collecting scientific information, including images of Ceres at a resolution of 35 meters per pixel.
Dawn mission specialists presented a new image of mysterious spots on the asteroid Ceres for public viewing. To date, this image is the closest and most detailed look at the Okator crater, where these mysterious features are located. The image resolution is 140 meters per pixel.
September 10, 2015
From the orbit in which the vehicle was located, the shapes of the brightest central spot, as well as other features of the crater itself, are already very clearly visible. But, since these spots are still much brighter than the underlying surface, experts in the presented image actually combined two frames: one frame was correctly exposed to study the spots, and the other so that the bottom of the crater could be seen.
“Thanks to Dawn Station, we were able to transform a distant, strange spot into a complex, beautiful and breathtaking landscape right before our eyes. Very soon, scientific analysis will reveal the geological and chemical nature of this mysterious and hypnotic extraterrestrial landscape,” Mark Reiman, chief engineer of the Dawn mission.
The spacecraft has now completed two eleven-day cycles of mapping the surface of Ceres, and began a third on September 9, 2015. In total, over the next two months, Dawn created a surface map six times, and each cycle consists of 14 orbits. By creating maps of each orbit from a slightly different angle, scientists will eventually be able to create stereo images and a fully three-dimensional view.